Patent GB-921041-A (GB)
Title: Resins prepared from polyspiranes and an isocyanate material
IPC: C08G4/00
Filed: 1959-04-16
Abstract: A hydroxy-containing polyspirane, of molecular weight 400-20,000, and which is the reaction product of pentaerythritol (if desired containing up to 50% by wt. of dipentaerythritol) with a dialdehyde or acetal thereof or a diketone or ketal thereof is reacted with a polyisocyanate or derivative thereof.  Suitable polyspiranes are poly(glutardiylidene pentaerythritol), poly(3-methylglutardiylidene pentaerythritol); poly(malondiylidene pentaerythritol), or may be prepared from succinaldehyde, adipaldehyde, pimelic dialdehyde, suberic dialdehyde, azelaic dialdehyde, sebacic dialdehyde, cyclopentanedial, cyclohexanedial, phthalic aldehydes, methyl and ethyl diacetals of malon-, succin-, or glutar-aldehyde; or from methyl and ethyl diketals of 2,4-pentanedione, 2,5-hexanedione or 2,6-heptanedione.  Mixtures of these compounds may be used if desired.  Suitable polyisocyanates or derivatives may have the formula R11(N=C=O)z where R11 is an aliphatic hydrocarbon radical of 2-8 carbon atoms or a cyclic hydrocarbon radical of 5 or 6 carbon atoms or an alkyl-aryl substitute thereof and z is 2, 3 or 4.  Dimers or trimers of polyisocyanates may be used, e.g. a trimer of the formula:-  <FORM:0921041/IV(a)/1> Some or all of the isocyanate groups may have been reacted with compounds containing one or more active H atoms, yielding derivatives with the formula:- <FORM:0921041/IV(a)/2> in which B is the residue of a substance containing an active H atom, and D+E is not more than 4.  Sterically hindered isocyanates according to U.S.A.  Specifications 2,723,265 or 2,729,666 may be used.  A suitable material may also be made from 1 mol. of trimethylol propane and 3 mols. of tolylene diisocyanate.  A list of suitable simple polyisocyanates is given.  In typical examples (1) technical pentaerythritol (containing 12% of the dimer) is refluxed with glutaraldehyde in presence of oxalic acid as catalyst.  The resulting poly(glutardiylidene pentaerythritol) resin is dissolved in a hot mixture of cresylic acid and naphtha, filtered and mixed with a cresylic acid-naphtha solution of the phenol adduct of a condensate from 1 mol. trimethylol propane and 3 mols. tolylene diisocyanate to form a wire enamel.  (2) is similar with the addition of a small quantity of poly(tetrafluorethylene) to the enamel.  Other examples describe the preparation of poly(malondiyledene pentaerythritol); poly(terephthaldiylidene pentaerythritol); poly(succindiylidene pentaerythritol), and of a copolymer from pentaerythritol and an equimolar mixture of glutaraldehyde and 3-methyl glutaraldehyde.  Blocked isocyanates give enamels of greater storage life.  If unblocked isocyanates are used, they should be mixed with the polyspirane resin at below 40 DEG C.  Solvents which may replace the naphtha are chlorbenzene, toluene, cumene, furfuryl alcohol or furfural.  Some of the physical properties of insulating coatings of the enamels on wires are set out in the Specification. Uses: Electrical insulation generally, e.g. wire coating, slot liners, encapsulation, sheet insulation; impregnating varnishes for glass tape or electrical coils; chemically resistant surface coatings.